BRPI0822369A2 - zinc-based coated steel sheet excellent for surface electrical conductivity having a corrosion preventive thin film layer - Google Patents

Abstract

zinc-based coated steel plate excellent in surface electrical conductivity having a corrosion preventive thin film layer the present invention relates to a zinc-coated or zinc alloy steel plate expressing performance provided as much as corrosion resistance for conductivity. The zinc-coated or zinc-alloy steel plate of the present invention is a zinc-coated or zinc-alloy steel plate having a roughness average of the surface of the zinc-coated layer defined by jis b 0601 obtained by a meter. jis b 0651 stylus-type surface roughness from 0.3 µm to 2.0 µm and a maximum peak height rp of 4.0 µm to 20.0 µm, where the average roughness ra (peak) obtained by measuring whether the 20 µm length range of the peak portions of 80% or more of rp by an electron ray roughness analyzer is 70% or more of the average ra (average) roughness obtained by measuring the An evaluation of the length of 20 µm of parts of a height of ± 20% about a midline obtained by a stylus-type surface roughness meter, by an electron ray roughness analyzer.

Description

Invention Patent Specification Report for ’‘ EXCELLENT ZINC-BASED STEEL PLATE IN ELECTRICAL CONDUCTIVITY ON THE SURFACE HAVING A PREVENTIVE THIN FILM LAYER AGAINST CORROSION

TECHNICAL FIELD

The present invention relates to a steel plate with a zinc-based surface used for PCs, audio, TV, and other household equipment and copiers, printers, faci-facies, and other office automation products that are superior in conductivity of the surface 10 of the steel plate, which becomes essential to guarantee the grounding performance and electromagnetic shielding of the steel plate members after the assembly of the electronic household appliances or office automation products, and is also provided with corrosion resistance. BACKGROUND OF THE TECHNIQUE

For a long time, a surface-treated steel sheet comprised of a chromate-treated galvanized steel sheet on its surface was used in large quantities for industrial products in a wide range of fields. This galvanized steel sheet had a high capacity for suppress the formation of white rust that occurred when used under the usual atmospheric environment and also had the characteristics of easily guaranteeing the conductivity between the electronic plate and the steel member and having a superior performance of grounding and shielding capacity. of suppressing white rust was high, it was believed, due to the high passivation capacity of a 25 chromate film for zinc-coated material and the high capacity of the film to repair the damage. In addition, the conductivity was good since the chromate-treated layer was thin and uniform, so the contact resistance with the conductive terminals was kept low.

In recent years, the demands for materials for the reduction of 30 substances of environmental load and toxic substances have become more rigid. There is an increasing movement in the direction of restricting the use of hexavalent chromium used for chromate films. Hexavalent crema is a toxic substance identified as being carcinogenic. The restrictions on the discharge of hexavalent chromium in the process of production of steel sheets with treated surface are considered and the damage to health that accompanies its elution when using the steel sheet.

Therefore, the inventors developed a treated film that uses absolutely no chromate (for example, see JP 2000-319787 A). JP 2000-319787 A described the technology of coating the surface of a galvanized steel sheet with a layer of rust prevention coating. To improve corrosion resistance, phosphoric acid or an inhibiting ingredient was added properly. This treated steel sheet was superior in corrosion resistance due to the fact that it was coated with an insulating resin layer. but it had the defect of being inferior in conductivity of the surface. Therefore, the JP 2000-319787 A rust-proof steel sheet cannot currently be considered to have sufficient characteristics for application in household electronic equipment, office automation products, and other equipment that emphasize grounding capacity.

Here, 'grounding capacity' means making the potential of the steel sheet surface caused by electromagnetic waves emitted by electronic components or electromagnetic waves coming from outside the equipment, the same potential of the earth. If this grounding capacity is insufficient, problems such as erroneous operation or malfunction of the electronic equipment, noise, etc. will occur.

Electronic equipment has so far guaranteed this earthing capacity when screwed to steel frames. chassis, etc. In this case, the finishing faces of the steel sheets were exposed in the screw holes, so the metal-to-metal conduction can be easily obtained regardless of any chromate layer. However, together with the increasing miniaturization and higher performance of electronic equipment in recent years, the number of complicated shaped parts has increased, the screwed parts have decreased and the parts have been increasingly linked by steel surface contact, or • ¹⁰ contacts per spring bundle sealing. In this case, it is important that the surface of the coated steel sheet has less contact resistance. In the systems coated with insulating resin explained above, the earthing capacity has therefore become insufficient.

As a prior technique to improve this earthing capacity, JP 2004-277876 A forms an intermediate layer having a earthing capacity on the surface of the coating layer and also forms a layer of organic resin on its surface and specific that the coverage rate of layer of organic resin is at least 80% and for the roughness of the steel plate surface, an arithmetic mean of the roughness Ra is 1.6 to 2.0, one and the waviness filtered in the center line Wca is no more than 0, 8 pm.

In addition, JP 2005-238535 A describes the technique of obtaining a surface roughness of a plate to be coated by defining the surface roughness Ra and PPl of the hardening lamination cylinders treated with electrocoat and guaranteeing the conductivity of the plate. resulting galvanized steel obtained without impairing corrosion resistance.

In addition, JP 2002-363766 A defines the surface roughness of the plate itself to be coated by counting the peaks and Ra in order to achieve both corrosion resistance and conductivity.

However, although JP 2004-277876 A. to JP 2005-238535 A, and JP 2002-363766 A all demonstrate a conductivity improvement effect, performance is not stably expressed and, depending on the production line, conductivity is not can be guaranteed. The development of a technology that steadily guarantees conductivity was desired.

Galvanized steel sheet coated with a chromate-free film is produced by subjecting the coil-shaped steel sheet continuously to a coating treatment and a chromate-free treatment. The coating method includes electrodeposition and hot dip coating. The first is the technique of electrochemically causing the precipitation of zinc in an aqueous solution containing zinc ions, while the last is the technique of immersing the steel sheet in a molten zinc bath to form a film. The coating surface configuration is. in the case of electrodeposition, high in uniformity of coating formation, then the configuration of the sheet surface is maintained, but with hot dip coating, the planing property is high and the configuration is generally transmitted by transferring the configuration of the cylinder hardening lamination after coating. The coated steel sheet is coated with a chromate-free or inorganic-based film or a cremate film, cooked, and dried by one. post-treatment section. After that, it is cooled to obtain the final product.

DESCRIPTION ΏΑ INVENTION

A sheet of steel coated with zinc or a zinc alloy produced by such a production process can contact a large number of metal cylinders in the production process. Depending on the cylinders, the surface of the steel sheet is often subjected to a relatively high grinding force. If the coated surface is laminated by metallic cylinders after galvanizing and before coating in the post-treatment section, there is a good chance of changing the configuration of the coated surface. The galvanizing metal has a roughness of about 60 or similar, that is, it is soft, so the portions that protrude from the coating are often compressed until they are flat by the metal cylinders. Such deformation occurs in the microscopic region, so it is often not possible to sufficiently recognize changes in configuration by measuring with a stylus-type surface roughness meter defined in JIS B 0651. Furthermore, with such flattened configurations, the plate roughness or the the roughness transmitted by the hardening cylinder on the plate after coating ends up changing and the state of the surface coverage of a primary layer of rust preventive coating also changes, so a sufficient conductivity can no longer be expressed.

that is, the issue has been to avoid the drop in conductivity due to the compression of the parts that protrude from a coated surface caused by the current production process using a continuous coating equipment for galvanizing and after-treatment.

The inventors engaged in in-depth studies to achieve both conductivity and corrosion resistance of a sheet coated with zinc or zinc alloy treated without chromate. As a result, they found that it is possible to achieve both conductivity and corrosion resistance not by managing the surface roughness of a layer coated with zinc or zinc alloy by measuring the roughness parameter defined in JIS B 0601 using the equipment defined in JIS B 0651, but by the definition of the roughness of the microscopic region of the projected parts of the coating. In addition, they found that the ratio of portions with a roughness equal to or greater than a certain value being at least an early value is also important. The present invention is made on the basis of the above finding.

That is, the essence of the present invention is as follows:

(1) A sheet of steel coated with zinc or higher zinc alloy in surface conductivity after being given a thin film of a primary layer of rust preventive coating having a medium roughness Ra of a surface of a defined zinc-coated layer by JIS B 0601, obtained by a stylus surface roughness meter defined by JIS B 0651. from 0.3 pm to 2.0 um and one. maximum peak height Rp from 4.0 pm to 20.0 pm, where the average roughness Ra (peak) obtained by measuring the 20 pm evaluation length range of the peak parts of 80% or more of the Rp by 25 um 3D electron ray roughness analyzer is 70% or more of the average (average) roughness obtained by measuring the 20 pm evaluation length range of parts of a height of ± 20% in about a midline, obtained by a stylus-type surface roughness meter, by a 30-electron 3D roughness analyzer, (2) A sheet of steel coated with zinc or zinc alloy superior in conductivity of the surface after a thin film of a primary layer of preventive coating centers the rust as shown in item (1). where the area of the parts where the average Ra (peak) roughness obtained by measuring the 20 pm evaluation length range of the peak parts of 80% or more of the Rp defined by 5 JIS B 0601. obtained by the type roughness meter stylus, by an electron ray 3D roughness analyzer is less than 70% of the average roughness Ra (average) obtained by measuring the length range of the 20 pm evaluation of parts at a height of ± 20% on about one line average, obtained by a stylus-type surface roughness meter, by a 3D electron radius roughness analyzer è 5% or less of the zinc-coated surface area as a whole (3) A zinc-coated steel plate or superior zinc alloy in surface conductivity after a thin film of a primary layer of rust preventive coating is given as shown in items (1) or (2), where the average roughness Ra (peak) obtained by measuring the range of evaluation of the 20 pm length of the peak parts of 80% or more of the Rp defined by JIS B 0601. obtained by a stylus-type surface roughness meter, by 20 an eietron 3D roughness analyzer is 0.03 pm a 1.0 pm.

(4) A sheet of steel coated with zinc or higher zinc alloy in surface conductivity after a thin film of a primary layer of preventive rust preventive coating is given as presented in any of items (1) to ( 3), where the average thin film thickness of the rust preventive coating layer is 0.2 um to 5.0 pm.

(5) A method of producing a zinc-coated steel sheet or superior zinc iiga in surface conductivity after a thin film of a primary rust preventive coating layer is given, the aforementioned zinc-coated steel sheet or zinc alloy produced by coating a steel sheet with

The ^'10 zinc or zinc alloy, and then forming a thin film of a primary rust preventive coating layer, the aforementioned zinc or zinc alloy coated steel sheet having an average roughness Ra of the surface of the coated layer zinc defined by JIS B 0601, obtained by a stylus surface roughness meter by JIS B 0651, from 0.3 pm to 2.0 pm and a maximum peak height Rp from 4.0 pm to 20.0 pm, an average roughness (Ra) (peak) obtained by measuring the 20 pm length evaluation range of the peak parts with 80% or more of the Rp by a 3D electron ray roughness analyzer with 70% or more of the roughness mean Ra (mean) obtained by measuring the 20 pm length assessment range of parts of a height of ± 203 'over a midline, obtained by a stylus-type surface roughness meter, by a 3D roughness analyzer of electron rays, the mentioned method characterized for controlling the iamination force so that the ratio where the Iamination force F (N / mm ² ) per mm of cylinder length applied to a coating surface by puller cylinders that contact the transported steel plate and the hardness microvickers MHv of the coating layer measured by JIS Z 2244 satisfies the relationship (1) following where the steel sheet is supplied with the zinc coating layer for the formation of the thin film of the primary coating layer against rust ·.

F <9.8065MHv x (R ² - (R-fv1O Y) ⁰⁶ (1) where R is the radius of the cylinder (mm), and h is the value of Rp of the coated steel sheet (pm).

According to the present invention, even if the thickness of the primary thin film of the rust preventive coating layer is made thicker, the conductivity is expressed, so this is achieved together with the corrosion resistance. In addition, if it is possible to make the layer thicker, not only the resistance to corrosion, but also the ability to work by pressing, the ability to transmit crack resistance, resistance to ablation, and other characteristics are also improved. In addition, by controlling production using the roughness of the coating of the present invention as an indicator, it is possible to produce a steel sheet coated with zinc or zinc alloy, which is stable in conductivity and corrosion resistance, 5 even in production. in several coating lines.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a photomicrograph by electronic scanning of the surface of an electrocoivanised steel plate.

Figure 2A is an image composed of combined 4-channel signals for a 3D electron ray roughness analyzer.

Figure 2B is a 3D image analyzed from part (1) of figure 2A.

Figure 2C is an angled 3D image of the vicinity of part (1) of figure 2A.

Figure 3A is an electronically scanned microphotograph of a cross section of an electrogivanised steel sheet covered with a thin film of rust preventive primary layer without the microcrisals of the projected parts of the sheet being compressed,

Figure 3B is an electronically scanned photomicrograph of a cross section of an electroplated steel sheet covered with a primary layer of rust-preventive thin film with the parts that project the compressed sheet coating microcrystals. BEST MODE FOR CARRYING OUT THE INVENTION

Details of the present invention will be explained below.

The inventors examined in detail the configurations of the coated surfaces of the zinc-coated steel sheets or zinc alloy sheets produced by continuous coating equipment. An example of an electronically scanned photomicrograph of the surface of an electroplated steel sheet produced in an electrogalvanizing line is shown in figure 1. The inventors found that the coating layer is formed along the configuration of the sheet relief transmitted by the lamination hardening and that the surface of the coating layer has a micro configuration caused by the forms of micro crystals of the etetrogalvanization layer itself. However, they found that the configuration caused by the forms of microcrystals on the surface of the coating layer formed on the projected parts of the plate includes flat portions due to compression. The portion is shown by the dark contrast indicated by the arrow in the figure. The roughness of the compressed portion cannot be measured by a stylus-type surface roughness meter defined by JÍS B 0651 .. That is, a stylus-type surface roughness meter uses a metal stylus as a measuring instrument, and the radius 10 of curvature R of the front end of the stylus is about 5 pm. so it is not possible to detect the micro-crystal forms caused by the coating crystals of figure 1. Therefore, the inventors have intensively studied the technique for measuring such forms of microcrystals and as a result have found that it is sufficient to use a roughness analysis system15 using a 3D scanning electron microscope.

Figure 2A to Figure 2C show the measurement results using a 3D field emission electron ray roughness analyzer (ERA-8900FE) produced by Elionix .. This analyzer is equipped with a secondary electron ray detector of 4 channels and can quantify the relief of the surface. As a result, the resolution of the roughness analysis is extremely high, and it is 1 nm in the height direction and 1.2 nm in the flat direction. It is possible to measure the microforms of the coating crystals of figure 1 sufficiently.

The photograph in figure 2A is an image composed of signals with 25 bits of the 4 channels. The dark contrast part in the figure (area of (1) in the figure) is the region of the projection of the ohapa. The coating layer is compressed and flattened there. On the other hand, the neighborhood area part represents the compressed part of the plate, where the microcrystalline forms of the coating layer are maintained. The micro configurations of these areas 30 are shown in figure 28 and figure 2C respectively.

In addition, to quantify the surface configuration in the local regions based on these digital image data, the Ra value was found in the region of the evaluated length 20 pm. The Ra of the compressed area (1) in figure 2A was 0.02 pm, while the Ra of the other parts was 0.06 pm. That is, by measuring the roughness in the extremely narrow range of the 20 pm length assessment, the compressed parts that protrude and the other parts where the microcrystals of the coating remain differ in Ra for a ratio close to 3 to 1, while it was possible to clearly indicate the difference in roughness,

Next, the inventors studied in detail the effects of such microconfiguration of the parts that protrude from the sheet in the state of covering the surface of a primary thin film of rust preventive coating. The inventors coated a coated steel sheet without the micro coating crystals of the sheet of the parts that are projected to be compressed and a steel sheet with the same compressed with water-based polyolefin resin coatings until 1.2 pm and examined their cross-sectional structures by a scanning electron microscope. The results are shown in figure 3A and figure 3B. The resin - coated layer of the coated steel sheet of non - compressed Figure 3A becomes thin at the projecting parts of the plate. In addition, in the parts protruding from the microcrystals on the surface of the coating layer of those parts, a state has been observed where the resin-coated layer does not completely cover the surface. On the other hand, the inventors found that in the compressed coating of the projecting parts of the plate of figure 3B, the resin-coated layer became thin, but completely covered the surface. That is, if there are forms of microcrystals on the surface of the coating layer of the projecting parts of the sheet, they act to decrease the coverage of the resin layer and partially expose the coating layer. These exposed parts become conduction points, so the inventors found that the conductivity was guaranteed by the contact of the steel plates with each other or by contact with a conductive terminal. On the other hand, the inventors found that the parts where the micro configuration of the coating layer on the projecting parts of the sheet are compressed are covered by the insulating resin film, so no conductivity was expressed. That is, the inventors found that to improve the conductivity of the electro-galvanized steel sheet, just controlling the configuration of the sheet's relief is not enough and that it is important to leave = a crystalline microstructure on the surface of the coating layer of the projecting parts.

The present invention was made on the basis of these technical discoveries. The inventors used it as an indicator to define the residual degree of microconfiguration on the surface of the coating layer of the projecting parts of the Ra value of an evaluation length of 20 10 pm of the different parts of the projecting parts and found that the Ra value of the projecting parts of the sheet is 70% or more, compression does not occur or there is some compression, but there is no effect on conductivity.

The reasons for limiting the numerical values of the present invention will be discussed below.

Initially, the surface roughness of the coated steel plate shown by a standard stylus type roughness meter is, in terms of average roughness Ra defined by JIS B 0601, 0.3 pm to 2.0 pm. If a. Ra is less than 0.3 pm, the primary thin film surface coverage of the rust preventive coating layer becomes good. This is desirable from the standpoint of corrosion resistance, but it is not preferable from the standpoint of conductivity. As a result, adjusting the primary thin film thickness of the rust preventive coating layer to achieve both conductivity and corrosion resistance is difficult. On the other hand, if Ra exceeds 2.0 pm, the coverage 25 of the primary thin film of the corrosion preventive film becomes extremely poor, and the conductivity becomes extremely good, but the corrosion resistance deteriorates. Thus, it is no longer possible to adjust a film thickness range where both are reached. Therefore, Ra was determined to be 0.3 pm to 2.0 pm. Preferably, Ra is 0.6 to 30 1.5 pm, more preferably 0.6 to 1.1 µm, most preferably about 0.9 pm. The peak peak height Rp, for reasons similar to Ra, was also determined to be 4.0 um at 20.0 pm. Preferably, Rp is 12 to 20 µm, more preferably 12 to 17 pm. more preferably still about 15 pm.

If the zinc-coated or zinc-alloy steel plate has a coating deposition of less than 5 g / min, the action of resistance to sacrificial corrosion in relation to the steel plate becomes insufficient and red rust occurs in a short time. , so this is not preferable At 300 g / m ^z or more, the improved corrosion resistance effect ends up becoming saturated, the cost of the coating increases, and peeling occurs in the form of powder from the coating, so this is not preferable .

To define the forms of microcrystals in the coating of the parts that protrude from the plate, the inventors noted the peaks of 80% or more of the Rp and defined the Ra in the range of 20 pm evaluation co-length of those parts. In parts of less than 80% of Rp, there was no contact with the metal cylinders. Furthermore, if they are less than the 20 pm evaluation length, the error measurement can no longer be ignored, while if it is greater than 20 pm, the evaluation length can go beyond the limits of the projecting plate parts and ends up including compressed parts, so this is not preferred,

For parts other than those projecting, the parts

20% above and below the neighborhood of the midline were used for representative values. The Ra (average) value of these parts was taken as the standard value. The inventors found that if the Ra (peak) of the projecting parts of the plate (peak parts) is a value of 70% or more of that value, either there is no compression by the metal cylinders or just a slight compression and there is no effect on conductivity and corrosion resistance. On the other hand, the inventors found that if the Ra value of those parts becomes less than 70%, the compression by the metallic cylinders becomes remarkable. The upper limit of the Ra (pioo) / Ra (average) ratio is determined to be 110% since the greater the transfer of roughness30 from the cylinders, the greater the drop in the capacity for continuous operation due to the zinc sheath around the cylinders etc. Preferably the Ra (peak) / Ra (average) ratio is 70% to 110%, more preferably 95% to 105%, most preferably 100% crown.

If the peak parts become very small in Ra (peak), they end up being completely covered by the primary thin film of the rust preventive coating layer and no surface conductivity is expressed, then the lower limit of Ra (peak) has been determined to be 0.03 um. On the other hand, if the Ra (peak) becomes too large, the coverage rate of the coating film falls, and the conductivity of the surface is improved while the corrosion resistance deteriorates, then its upper limit has been determined to be 1 , 0 pm. Preferably, the Ra (peak) is 0.03 to 1.0 pm, more preferably 0.03 to 0.5 pm. preferably still about 0.2 pm.

In addition, the inventors have found that even if there are compressed parts in the projecting parts of the plate (Ra less than 70%). if the area ratio of these parts is not more than 5% of the zinc-coated surface area as a whole, a material of the present invention is obtained which achieves both conductivity and corrosion resistance. If the area ratio becomes greater than 5%, the characteristics of the compressed parts have become dominant and the drop in conductivity has become a value that cannot be ignored. The area ratio is more preferably 3% or less, more preferably still 1% or less.

To get out of the microcrystalline forms of the protruding parts of the sheet, optimization of various operating conditions is necessary, but the most important thing is to avoid strong lamination by the metal cylinders after coating until the formation of the primary thin film of the layer of rust preventive coating, If the cylinders are winding cylinders, the rolling force is small and no compression occurs, but in the case of pull cylinders where the steel plate is also contacted by the contact line, the upper limit of the force rolling mill must be controlled.

At that time, the upper limit where the Vickers hardness of the coating layer prevents compression from occurring differs, but the hardness of the coating layer changes easily according to the conditions of trolysis or the concentration of impurities in the bath. so it is not effective to define the rolling force of metallic cylinders across the plate. The inventors studied in detail the permissive upper limit value! of the rolling force of the cylinder and as a result found a relationship defining the upper limit of the rolling force. That is, when the rolling force per mm of cylinder length is F (N / mm ^z ) and the microvicker's hardness of the coating layer measured by JIS Z 2244 is MHv, the following relationship occurs:

F <9.8065MHv x (R <(R-hx10'Y) ° ⁵ (1) where, R is the radius of the cylinder (mm), while h is the value of Rp (pm) of the coated steel sheet.

If F becomes greater than the value on the right side of formula (1), the coating layer becomes compressed, so this is not preferred. If it is less than the value on the right side, the shapes of the projecting parts defined by the present invention can be maintained. In formula (1), if the standard MHv of the pure zinc coating is 50, the radius of the pull cylinders is 100 mm, and the Rp of the coated steel sheet is 10 pm, the right side becomes 693. On the other hand On the other hand, the rolling force of standard pull cylinders is 1000 to 3000 (N / mm ² ) or similar. Thus, under conditions of ordinary operation, the rolling force ends up becoming a greater value on the right side and compression occurs. Therefore, it is necessary to control the rolling force in order to satisfy the formula (1) discovered by the present invention.

It is important that the primary thin film of the rust preventive film is adjusted to a thickness that achieves both conductivity and corrosion resistance. The smaller the Ra of JIS B 0651 on the sheet, the smaller the optimum film thickness. This value cannot be specified, but when Ra is 0.3 um, a minimum of 0.2 pm is required. On the other hand, when Ra is 2.0 pm, a maximum of 5.0 pm is allowed. Therefore, the lower limit and the upper limit of the film thicknesses were determined to be 0.2 pm and 5.0 pm. However, there are several optimal values due to the effects of a number of factors such as the shape of the plate, the Ra and Rp roughness of the microcrystals of the projecting parts, the type of coating, etc.

The primary thin film of the rust preventive layer can be of any type such as water-based resins such as acrylics, olefins, urethanes, styrenes, phenols, polyesters, etc. or solvent-based epoxides, etc. Alternatively, it can be based on inorganic silica, soluble glass, metallic salt, (an oxide of Zr, Ti, Ce, Mo, or Mn). In addition, it can be based on an organic-inorganic compound silane agglutination agent. The film may have added phosphoric acid, an inhibitory ingredient, or Co, Ni, or other metals to improve corrosion resistance and improve blackness resistance.

A single-layer treatment of only the primary thin film of the rust preventive film gives sufficient performance, but if a treatment of the inner layer comprised 15 of a treatment of the chromate-free inner layer is also applied, the pink color resistance, coating adhesion, and other aspects of film performance are much more improved, so this is preferable. As a treatment agent for the chromate-free inner layer, Zr oxide, Ti oxide, Si oxide, EC oxide, a phosphate, a silane bonding agent, etc. can be selected. If the amount deposited is 0.001 g / m ² or less, sufficient performance cannot be obtained, while if it is above 0.5 g / m ^: -, the effect becomes saturated and the adhesion resistance falls reciprocally and other problems of surface.

Examples

In the following, the present invention will be explained on the basis of examples.

An electrogalvanized steel sheet was prepared under the following conditions. For the plate, a cold-rolled steel plate with a thickness of 0.8 mm was used. The surface roughness of this sheet was adjusted by changing the roughness of the lamination cylinders used in the skin pass laminator after continuous annealing. The cylinder's roughness was given by a dull discharge process. This plate was φ 10 electroplated using electroplating equipment. The electrogalvanization was carried out in an acid bath of zinc sulfate at a current density of 50 to 100 A / dm ² at a line speed of 50 to 120 m / min.

The hot dip galvanized steel sheet was prepared under the following conditions. For the plate, a cold-rolled steel plate with a thickness of 0.8 mm was used. This sheet was hot dip galvanized using hot dip galvanizing equipment. The zinc bath was a Zn bath with Al 0.2% by weight of a temperature of 460 C. ^c reduced plaque in a reducing atmosphere of hydrogen-nitrogen to 800 ^C and was cooled to a temperature 480X and was then immersed in the bath. Two seconds after immersion, it was removed and dried by nitrogen gas to control the amount of coating deposited. The line speed was 100 m / min. The surface was given a roughness by an inline hardening lamination cylinder after coating.

The coated surface configuration was measured according to JIS B 0651. The equipment used was a Surfcom 1400A stylus surface roughness meter produced by Tokyo Seimitsu. In addition, the roughness of the microscopic region was measured using a 3D field emission electron ray roughness analyzer (ERA8900FE) produced by Elioníx.

The rolling force of the metal cylinders for the coating section after the coating is changed from the opening up to 3000 N / mm to change the state of the projecting parts of the plate. The thin - film primary coating against rust preventive is coated by a roll coater to a film thickness of 0.1 to 6 and one baked in a drying oven to a sheet temperature of 150 ^C C. For coating resin, a polyolefin resin ('' Hitec S-7024 '* produced by Toho Chemical} was added to pure water to give a solid resin concentration of 20% by weight, ammonium phosphate was dissolved to give a concentration of acid ions phosphoric of 1 g / l, and then 10 water-based silica (Snowtex N produced by Nissan Chemical) was added in an amount of 25 g / l to obtain a primary rust preventive coating agent. , for the coating based on inorganic resin, CT-E300N produced by Nihon Parkerizing was used. For the inorganic coating, a primary rust preventive coating agent was prepared by adding 50% powder. eso of fluorozonic acid and 50% by weight of a silane agglutination agent to pure water and adjusting the pH by phosphoric acid to 3.0.

The corrosion resistance of the specimen obtained was judged by corroding the part using the salt water spray method of JIS Z 2371 for 72 hours and determining the white rust area rate on the surface. A white rust of 1% or less was rated as A, one of 5% or less as Έ, and one greater than 5% with C ”. A ”and” B were designated as approved and C as failed. Conductivity was measured by a LORESTA EP produced by Mitsubishi Chemical. The contactor was an ESP type (type 4-proof) with a front end of the contactor with a diameter of 2 mm and a distance between the terminals of 5 mm. The number of times of conduction at a surface resistance of 1 κιΩ or less was judged by a contact load of 1.5 N / contactor and a test current of 100 mA between 20 times in different positions. Driving 20 times was rated as A, driving 10 to 19 times as B, and nine times or less as C. A and 8 were designated as pass and C as failed.

Table 1 shows the surface properties of the coating layer and the surface properties of the coating layer in the microscopic region, while Table 2 shows the data of the coating layer and the primary thin film of the rust preventive coating layer. Examples 1 to 39 are examples of the present invention.

Table 3 summarizes the results of the evaluation of corrosion resistance after 72 hours of SST and the results of the evaluation of the conductivity of the surface. Examples 1 to 39 are excellent in both corrosion resistance and cc-nductivity at all levels, while Comparative Examples 1 to 10 are poor in either corrosion resistance or conductivity and do not achieve both performances.

Table

No. Coating earn surface area configuration Surface properties of the microscopic lining layer Frog, one Rp, pm Ra (ρ <co) / Ra (mean), % Part of peak Ra. one Area ratio of pica Ra part / part of Ra average line 70% me less,% Ex. 1 0.3 4 100 0.2 0 Ex. 2 0.6 12 95 0.2 0 Ex. 3 1.1 15 98 0.2 0 Ex. 4 1.5 ......... · 17 95 0.2 0 Ex .. 5 2 20 105 0.2 (1 Ex. 6 0.9 15 70 0.2 0 Ex. 7 0.9 15 110 11 0 Ex. 8 0.9 15 100 0.2 5 Ex. 9 0.9 15 100 0.2 3 Ex. 10 0.9 15 100 0.2 .......................... 1 Ex. 11 0.9 15 100 0.2 1 Ex. 12 0.9 15 100 0.2 1 Ex. 13 0.9 ........ 15 100 0.2 1 Ex. 14 0.9 15 100 0.2 1 Ex. 15 0.9 15 100 0.2 1 Ex. 16 0.9 15 100 0.03 1 Ex. 17 0.9 15 100 0.1 1 Ex. 18 the 15 ... 100 0.5 1 Ex. 19 0.9 15 :: ................. 100 1 1 Ex. 20 0.9 15 100 0.2 1 Ex .21 0.9 100 0.2 1 Ex. 22 0.9 111 .......'......... 'i 100 0.2 1 '

No. Surface configuration of the coating layer Surface properties of the microscopic lining layer Frog, urn to B P Ra (peak) / Ra (mean),% Part of pice Ra, pm Area ratio of peak part Ra / part of Ra average line 70% or less,% Ex. 23 0.9 15 100 0.2 1 Ex. 24 0.9 15 100 0.2 1 Ex. 2.5 0.9 15 100 0.2 1 Ex. 26 0.9 15 100 0.2 1 Ex. 27 0.9 15 100 0.2 1 Ex .. 23 0.9 15 100 0.2 1 Ex. 29 0.9 15 100 0.2 1 Ex. 30 0.9 15 100 0.2 1 Ex. 31 0.9  15- 100 0.2 1 Ex. 32 0.3 4 100 0.2 0 Ex. 33 1.1 15 100 0.2 0 Ex. 34 O 17 100 0.2 0 Ex. 35 2. 20 100 0.2 0 Ex. 36 0.9 15 100 0.2 1 Ex. 37 0.9 15 100 0.2 1 Ex. 38 0.9 15 100 0.2 1 Ex. 39 0.9 15 100 0.2 1 Comp. Ex. 1 0.2 3 100 0.2 0 Comp. Ex. 2 2.2 ' 22 105 0.2 0 Comp. Ex. 3 0.9! 15 60 0.2 0 Comp. Ex. 4 0, $) 15 70 0.2 10 Comp. Ex. 5 0.9 15 100 0.2 1 Comp. Ex 6 0..9 15 100 0.2 1 Comp. Ex. 7 0.9 15 100 0.2 1 Comp. Ex. 8 0.9 15 100 0.2 1 Comp Ex 9 0.9 15 100 0.02 1

Surface properties of the microscopic lining layer

Super-1 surface configuration! re-sent! clothing |

Frog, pm Rp, pm: Ra (peak) / Ra (mean),% P Part of peak Ra, pm Area ratio of peak part Ra / part of Ra average line 70% or less,% Comp. Ex. 10 0.9 15 100 1.5 1 I

inorganic silane

No. Corrosion resistance Conductivity Grades Ex. 31 THE THE Ex 32 THE THE Ex. 33 THE THE Ex. 34 THE THE Ex. 35 THE THE Ex. 36 THE THE Ex. 37 THE. THE Ex. 38 THE THE Ex. 39 THE THE Ex.Comp. 1 THE ç................ Ex.Comp. 2 Ç THE Ex.Comp. 3 THE Ç Ex.Comp. 4 THE Ç Ex.Comp. 5 Ç THE Ex.Comp. 6 THE THE Peeling of powder coating _: bad Ex.Comp. I ^s Ç THE Ex.Comp. 8 : :: ...... THE Ç Ex.Comp. 9 THE Ç Ex.Comp, 10 Ç THE

INDUSTRIAL APPLICABILITY

The zinc-coated or zinc-alloy steel sheet of the present invention can be used as a steel sheet with superior treated surface in conductivity and corrosion resistance. In particular, it can be used for applications where surface conductivity is required such as copier housings, facsimiles, and other office automation equipment or PC housings, AV equipment, etc. where grounding is required.

Claims (5)

1. Steel sheet coated with zinc or higher zinc alloy in surface conductivity after a thin film of a primary layer of rust preventive coating having a medium roughness Ra of a surface of a zinc coated layer defined by J IS B 0601, obtained by a stylus surface roughness meter defined by dIS B 0651, from 0.3 pm to 2.0 pm and a maximum peak height Rp from 4.0 pm to 20.0 pm, where the roughness mean Ra (peak) obtained by measuring the 20 pm evaluation length range of the peak parts of 80% or more of the Rp by a 3D electron ray roughness analyzer is 70% or more of the average (mean) roughness obtained by measuring the range of the 20 pm evaluation length of parts of a height of ± 20% in about a midline, obtained by a stylus-type surface roughness meter, by a 3D electron ray roughness analyzer. 2. Steel sheet coated with zinc or higher zinc alloy in conductivity of the surface after a thin film of a primary layer of rust preventive coating according to claim 1 is given, where the area of the parts where the medium roughness String (peak) obtained by measuring the 20 pm evaluation length range of the peak parts of 80% or more of the Rp defined by JIS B 0601, obtained by the stylus type roughness meter, by a 3D radius roughness analyzer number of electrons is less than 70% of the average roughness Ra (average) obtained by measuring the length range of the 20 pm evaluation of parts at a height of ± 20% in about a midline, obtained by a surface roughness meter the stylus type, by a 3D electron beam roughness analyzer is 5% or less of the zinc-coated surface area as a whole, 3. Steel sheet coated with zinc or higher zinc alloy on the conductivity of the surface after a thin film of a primary layer of rust preventive coating according to claim 1 or 2 is given, where the average roughness Ra (peak ) obtained by measuring the 20 pm length evaluation range of the apex parts of 80% or more of the Rp defined by JIS B 0601, obtained by a stylus-type surface roughness meter, by a 3D roughness analyzer of electron rays is 0.03 pm to 1.0 pm. 4. Steel sheet coated with zinc or higher zinc alloy in conductivity of the surface after being given a Ona film of a primary layer of rust preventive coating according to any one of claims 1 to 3, where the average thickness of the Thin film of the rust preventive coating layer is 0.2. pm to 5.0 pm. 5. Method of production of a zinc-coated steel sheet or superior zinc alloy in surface conductivity after a thin film of a primary rust preventive coating layer is given, the aforementioned zinc-coated steel sheet or zinc alloy produced by coating a steel sheet with zinc or zinc alloy, and then forming a thin film of a primary rust preventive coating layer, the aforementioned zinc or zinc alloy coated steel sheet having an average roughness Ra of the surface of the zinc-coated layer defined by JIS B 0601, obtained by a stylus surface roughness meter by JIS B 0651, from 0.3 pm to 2.0 pm and a maximum peak height Rp of 4 , 0 pm to 20.0 pm, an average roughness (Ra) (peak) obtained by measuring the 20 pm length evaluation range of the peak parts with 80% or more of the Rp by a 3D ray roughness analyzer from el trons being 70% or more of the average roughness Ra (average) obtained by measuring the range, to assess the length of 20 pm of the parts of a height of ± 20% on a midline, obtained by a surface roughness meter of the stylus, by a 3D electron ray roughness analyzer, the aforementioned method characterized by controlling the lamination force so that the ratio where the lamination force F (N / mm ² ) per mm of cylinder length applied to a coating surface by pullers contacting the transported steel plate and the microvickers hardness MHv of the coating layer measured by JIS Z 2244 satisfies the ratio (1) following where the steel plate is supplied with the zinc coating layer for the formation of the thin film of the primary coating layer against rust ·. F <9.8065MHv x (R ² - (R-hx 10 ' ³ ) ² )' ^ui5 0) 5 where R is the radius of the cylinder (mm), and h is the Rp value of the coated steel sheet (pm).